1. Field of the Invention
The present invention relates to devices for locking a casement window. More specifically, the present invention relates to roller pins mounted on a tie bar where the roller pins engage corresponding keepers to lock the casement window at multiple points. Still more specifically, the present invention relates to an improved roller pin design that reduces friction between a roller pin and a corresponding keeper as the casement window locking mechanism is operated.
2. Description of Related Art
Casement windows are typically hinged along one side and swing closed into a fixed frame. One type of locking mechanism for casement windows uses a flat tie bar slidably mounted to the window frame along the open side of the window. The tie bar is provided with multiple locking pins that extend outward from the tie bar. A locking handle is provided on the interior of the window frame that can be thrown by the user between locked and unlocked positions. The locking handle slides the tie bar, which moves each locking pin between a corresponding locked and unlocked position.
The casement window sash is provided with multiple hook-shaped ramped keepers that move into position in front of the locking pins on the frame as the window is closed. The user then moves the locking handle to the locked position, which slides the tie bar and drives each individual locking pin into engagement with the hooked portion of a corresponding keeper.
One problem with older locking pin designs is friction and excess wear between the locking pin and the keeper. Friction can be particularly objectionable when multiple locking pins are simultaneously being engaged by their respective keepers as the locking handle is moved. A partial solution to this problem has been developed through the use of an outer cylindrical roller that rotates on an inner pin. The inner pin serves as an axle for the outer roller. The outer roller provides a low friction rolling contact between the inner hook portion of the keeper and the outer surface of the locking pin. A locking pin of this type is referred to herein as a “roller pin.”
In a conventional roller pin design, the inner pin is adjustably attached at one end to the tie bar and is provided with an end plate at the opposite end that is larger in diameter than the maximum diameter of the outer roller. The end plate is parallel to the tie bar. The outer roller, which is cylindrical, is loosely held between the end plate of the inner pin and the tie bar where it is free to rotate about the inner pin.
In this type of roller pin design, the end plate has a diameter that is greater than the inner width of the opening in the hook portion of the keeper. The keeper engages the outer roller of the pin and is held between the tie bar and the end plate. This increases security by preventing the keeper from being pulled over the end of the roller pin. A roller pin of this type is disclosed in U.S. Pat. No. 6,651,389 issued to Minter, et al. on Nov. 25, 2003.
However, because the end plate in this type of roller pin design is part of the fixed inner pin, it does not rotate with the outer roller. As the tie bar slides and the roller pins move into their respective keepers, the fixed end plates slide directly against a surface of the keeper producing friction and wear. When multiple roller pins and keepers are simultaneously being engaged, this friction becomes objectionable.
In prior art roller pin designs of the type described above the end plate on each roller pin is non-circular. It may, for example, be shaped as a square. This allows the installer to grip the end plate with a wrench or pliers and rotate the inner pin. The inner pin is eccentrically mounted to the tie bar and this rotation adjusts the location of the roller pin relative to the tie bar and the keeper.
Although this adjustment is effective, the non-circular shape of the end plate has several disadvantages. One disadvantage arises when the roller pins are visible. Each individually adjusted roller pin will have a different angular orientation. The non-circular end plates on different roller pins will not align with each other, or with the tie bar, producing a haphazard and unattractive appearance.
Another disadvantage to the non-circular shape of the end plate is that portions of the end plate extend farther out from the axis of the roller than other portions. This increases the contact area between the end plate and the keeper beyond the minimum necessary, thereby producing a further increase in undesirable friction.
Still another disadvantage is that the non-circular shape requires greater clearance between the end plate and other portions of the window to accommodate all possible orientations of the end plate.